This invention relates generally to medical electrical leads, and in more particular to cardiac pacing leads of the type combining pacing and pressure sensing functions on a single lead.
U.S. Pat. No. 4,407,296 issued to Anderson discloses an implantable pressure sensing lead in which the pressure transducer is mounted at the distal end of the lead, with the diaphragm oriented perpendicular to the axis of the lead. The diaphragm is protected by means of a slotted grill, which is intended to lie adjacent the tissue of the heart when the lead is implanted.
U.S. Pat. No. 4,485,813 issued to Anderson et al also discloses the incorporation of a pressure transducer into a cardiac pacing lead. In all illustrated embodiments, the transducer is generally cylindrical in configuration, carrying a pressure sensing diaphragm at its distal end, oriented perpendicularly to the axis of the lead. In some embodiments, the pressure sensor is located at the distal end of the lead. In these embodiments, an electrode having an aperture is located over the pressure transducer. In use, the electrode is intended to contact heart tissue. In other embodiments, the pressure transducer is located proximal to the distal end of the lead and includes a side facing aperture exposed to the surface of the diaphragm, through which pressure may be sensed. In both embodiments, the conductive case of the pressure transducer serves as part of the electrical path to the stimulating electrode located at the tip of the lead.
As discussed in the Anderson et al patent, location of the pressure transducer at the distal end of the lead is appropriate if the motion of the ventricular wall is the signal of particular interest. Location of the pressure transducer proximal to the distal end of the lead is desirable where blood pressure is the primary signal of interest.